This invention relates to an image display method and device for use in a game device or the like and, in particular, to the image display method which is appropriate for effectively and simply displaying a fluid flowing on a three-dimensional surface to obtain a sufficient visual effect. In addition, this invention relates to a computer-readable storage-medium for storing a program for simply displaying a fluid image.
Conventionally, a wide variety of computer games or video games, such a simulation game, a role playing game, a battle game, a puzzle game, and the like have been proposed and become popular in the world. It is a recent trend that the user""s demands or requests for the computer games have been also diversified and varied at every one of the computer games. One of the demands is to display, on a display device, a moving image with reality and to provide a visual effect such that the users would really be present in a game space. For example, it often happens in a certain computer game that displays must be made on the display device about a flame which appears at a predetermined position on a three-dimensional surface and which is spread from the predetermined position along the three-dimensional surface.
In order to display such a flame, a conventional computer game device usually prepares a plurality of bit map images of flames and switches them from one to another to seemingly display or express a flickering flame. In other words, an animation technique is used to display the flickering flame. However, the flickering flame due to the animation technique lacks reality of the displayed image as well as a variation of the flame.
Herein, it is to be noted here that a flame which spreads along a surface can be concerned with spread of an inflammable fluid and can be simulated by a flow or spread of the inflammable fluid. Taking this into consideration, a flame image with reality may be accomplished by hypothetically causing an inflammable fluid or fuel gas to flow on a predetermined curved surface or three-dimensional surface and by burning the inflammable fuel gas. In this event, the flame image might be required such that the flame which results from combustion of the fuel gas must be dynamically moved to cover a whole or a part of the three-dimensional surface, as the flow of the fuel gas spreads. It may be considered that a more efficient visual effect of a moving flame image can be achieved when flame size and color can be changed in response to a variation of a density of the fuel gas.
Otherwise, consideration may be made about replicating or simulating an actual phenomenon and event with a high fidelity by using a computer graphics technique or the like.
However, it is practically difficult to apply the computer graphics technique to a computer game device restricted in a memory capacity. In addition, the three-dimensional surface is located in a virtual space of the computer game device and is not practically present within a real space. Therefore, it is very difficult to simulate the moving flame on the three-dimensional surface on the basis of results obtained by observing the actual phenomenon and event.
It is an object of this invention to provide a method of simply displaying a fluid which is caused to flow along a virtual surface.
It is another object of this invention to provide a method of the type described, which is capable of successively displaying a flame which is moved together with the fluid and which is capable of changing a color of the flame to replicate the flame with a high fidelity.
It is still another object of this invention to provide a computer-readable storage medium which stores a program for displaying a moving flame with a high fidelity by changing the flow of the fluid and the color of the resultant flame.
It is yet another object of this invention to provide an image display device which can display a moving flame with a high fidelity.
According to an aspect of this invention, a method is for use in simply and artificially displaying, on a display device, a fluid flowing on a three-dimensional surface which has a predetermined configuration. The method comprises the steps of mapping a fluid start point defined on the three-dimensional surface onto a predetermined flat surface to decide a provisional start point on the predetermined flat surface, determining an initial fluid density at the provisional start point on the predetermined flat point, deciding a succeeding fluid density after lapse of a unit time at each position which is spaced in each prescribed direction from the provisional start point by a unit distance, so that the succeeding fluid density at each position is deceased in comparison with the initial fluid density at the provisional start point, successively calculating a next following fluid density at the provisional start point and each position each time when a next unit time lapses, re-mapping each of the succeeding and the next following fluid densities of the predetermined flat surface onto the three-dimensional surface as re-mapped results, and successively displaying the re-mapped results on the display device. In this event, each of the densities is concerned with a color of a flame to be displayed on the display device.
According to another aspect of this invention, an image display device is for use in displaying, on a display device, an image such that a fluid flows on a three-dimensional surface of a predetermined configuration. The device comprises mapping means for mapping a fluid start point defined on the three-dimensional surface onto a predetermined flat surface to decide a provisional start point on the predetermined flat surface, density calculating means for calculating an initial fluid density at the provisional start point on the predetermined flat point, together with a succeeding fluid density after lapse of a unit time at each position which is spaced in each prescribed direction from the provisional start point by a unit distance, decreasing means for decreasing the succeeding fluid density at each position and the provisional start point each time when a unit time lapses, re-mapping means for re-mapping each of the densities on the predetermined flat surface onto the three-dimensional surface as re-mapped results, and successively displaying means for displaying the re-mapped results on the display device.
According to a further aspect of this invention, a computer-readable storage medium is for storing a program which displays an image of a fluid flowing on a three-dimensional surface of a predetermined configuration. The program comprises the steps of mapping a fluid start point defined on the three-dimensional surface onto a predetermined flat surface to decide a provisional start point on the predetermined flat surface, determining an initial fluid density at the provisional start point on the predetermined flat point, deciding a succeeding fluid density after lapse of a unit time at each position which is spaced in each prescribed direction from the provisional start point by a unit distance, so that the succeeding fluid density at each position is deceased in comparison with the initial fluid density at the provisional start point, successively calculating a next following fluid density at the provisional start point and each position each time when a next unit time lapses, re-mapping each of the succeeding and the next following fluid densities of the predetermined flat surface onto the three-dimensional surface as re-mapped results, and successively displaying the re-mapped results on the display device.
According to another aspect of this invention, a method is for use in displaying, on a display device, a flame which is being spread with an expansion of a fuel. The method comprises the steps of displaying a red flame on a low density zone on which a density of the fuel is low and displaying a flame which includes green and blue in addition to red on a high density zone on which a density of the fuel is high.